Embodiments of the invention relate to a semiconductor memory device and a method of forming the semiconductor memory device. In particular, embodiments of the invention relate to a nonvolatile memory device and a method of forming the nonvolatile memory device.
A nonvolatile memory device retains data stored in the device even when there is an interruption in the supply of power to the device. A flash memory device can store data by selectively storing electric charge in a floating gate disposed between a control gate and a semiconductor substrate. In a flash memory device, adjacent floating gates may electrically interfere with one another. Thus, the floating gates need to be electrically shielded to reduce such interference. The control gate electrode is disposed between adjacent floating gates and on a device isolation layer in order to perform a shielding function. Since the control gate and an active region disposed under the floating gate may interfere with one another, the distance between an edge of the active region and the control gate electrode needs to be spatially uniform in the nonvolatile memory device. To meet that need, the thickness of the device isolation layer needs to be controlled such that it is spatially uniform in the nonvolatile memory device.